Reference ranges for the fetal cardiac circumference derived by cardio-spatiotemporal image correlation from 14 to 40 weeks' gestation.

OBJECTIVES

The purpose of this study was to construct reference ranges for the fetal cardiac circumference derived from volume data sets obtained by cardio-spatiotemporal image correlation.

METHODS

A prospective descriptive study was conducted on normal singleton pregnancies with certain dates from 14 to 40 weeks' gestation. All underwent cardio-spatiotemporal image correlation to acquire volume data sets for subsequent analysis. Cardiac circumferences were measured offline in a multiplanar view with 4-dimensional imaging software. The reference ranges were constructed against gestational weeks and the biparietal diameter as independent variables, using regression models for both the mean and SD.

RESULTS

A total of 678 satisfactory volumes were analyzed. Normal reference ranges for predicting means and SDs of the fetal cardiac circumference were established based on best-fitted equations. The mean cardiac circumference (millimeters) was modeled as a function of gestational age (weeks) and biparietal diameter (centimeters) as follows: cardiac circumference = -53.11 + 6.56 × gestational age - 0.035 × gestational age(2) (SD = 0.67 + 0.18 × gestational age) and -17.60 + 17.68 × biparietal diameter (SD = 1.651 + 0.61 × biparietal diameter). Equations for z score calculation were also provided, and percentile charts for predicting the cardiac circumference at various points of gestational age and biparietal diameter were constructed.

CONCLUSIONS

Normal reference ranges and z scores for the fetal cardiac circumference have been provided. These normative data may be useful tools for assessment of fetal cardiac size, especially in cardiomegaly due to fetal anemia.